Question

因此，我查找并尝试了一些将XML文件转换为CSV文件的方法。我尝试过的方法是：

XSLT：获取给定XML的XSLT，然后形成CSV。但这很难维护，因为我们不知道我们将获得哪种XML文件，这使其不是通用解决方案。
使用Apache Digester
SAXP和JAXP 上面两种方法的问题在于，它需要先定义Java对象，因此，创建这么多的类又成了瓶颈，因为我们不知道XML的模式。每次都会改变。
使用DocumentBuildFactory并一直解析。这适用于通用XML文件，但对于5MB到1GB范围内的文件速度较慢。我的XML文件肯定不会大于1GB。

除了我已经尝试过的这些方法之外，关于如何以编程方式并且比上面更快地实现它的任何想法？我看过几种在线工具，这些工具可以在非常短的时间内将任何XML文件转换为CSV文件，它们似乎适用于任何通用XML文件。有什么建议吗？

以下是可能出现的不同示例，它们可能也会发生变化：

    <?xml version="1.0"?>
<Company>
  <Employee id="1">
      <Email>tp@xyz.com</Email>
      <artist>Bob Dylan</artist>
    <country>USA</country>
  </Employee>

</Company>

这是最简单的一个。预期输出为：

Company/Employee/Email,Company/Employee/artist,Company/Employee/country,Company/Employee/_id
tp@xyz.com,Bob Dylan,USA,1

另一个例子

<?xml version="1.0"?>
<Company>
  <Employee id="1">
      <Email>tp@xyz.com</Email>
      <UserData id="id32" type="AttributesInContext">
<UserValue value="7in" title="Height"></UserValue>
<UserValue value="" title="Weight"></UserValue></UserData>
  </Employee>
  <Employee id="2">
      <Email>tp@xyz.com</Email>
      <UserData id="id33" type="AttributesInContext">
<UserValue value="6in" title="Height"></UserValue>
<UserValue value="" title="Weight"></UserValue></UserData>
  </Employee>
  <Employee id="3">
      <Email>tp@xyz.com</Email>
      <UserData id="id34" type="AttributesInContext">
<UserValue value="4in" title="Height"></UserValue>
<UserValue value="" title="Weight"></UserValue></UserData>
  </Employee>
</Company>

预期输出为

Email,UserData/UserValue/0/_value,UserData/UserValue/0/_title,UserData/UserValue/1/_value,UserData/UserValue/1/_title,UserData/_id,UserData/_type,_id
tp@xyz.com,7in,Height,,Weight,id32,AttributesInContext,1
tp@xyz.com,6in,Height,,Weight,id33,AttributesInContext,2
tp@xyz.com,4in,Height,,Weight,id34,AttributesInContext,3

这有点复杂。这样会变得更加复杂和嵌套，最大范围可达1GB。

Answer 1

您可以尝试使用Java StAX API进行此提议。

例如：

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;

import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;

public class XmlToCSV {

    public static void convert(InputStream xml, OutputStream csv) throws Exception {
        try (StringWriter header = new StringWriter(4096); StringWriter content = new StringWriter(4096)) {
            XMLInputFactory factory = XMLInputFactory.newInstance();
            XMLEventReader xmlEventReader = factory.createXMLEventReader(xml);
            XMLEvent xmlEvent;
            long nestingLevel = -1;
            StringBuilder line = null;
            while (xmlEventReader.hasNext()) {
                xmlEvent = xmlEventReader.nextEvent();
                switch (xmlEvent.getEventType()) {
                case XMLEvent.START_ELEMENT:
                    ++nestingLevel;
                    if (0 == nestingLevel) {
                        break;
                    } else if (1 == nestingLevel) {
                        line = new StringBuilder();
                    }
                    StartElement startElement = xmlEvent.asStartElement();
                    serializeElementHeader(header, line, startElement);
                    break;
                case XMLEvent.CHARACTERS:
                case XMLEvent.CDATA:
                    if (nestingLevel < 1)
                        break;
                    Characters chars = xmlEvent.asCharacters();
                    if (!chars.isWhiteSpace()) {
                        line.append(chars.getData());
                        line.append(',');
                    }
                    break;
                case XMLEvent.END_ELEMENT:
                    if (--nestingLevel == 0) {
                        header.write("0/");
                        for(int i= line.length()-1; ',' == line.charAt(i); --i) {                           
                            line.deleteCharAt(i);
                        }
                        content.write(line.toString());
                        content.write('\n');
                    }
                    break;
                default:
                    break;
                }
            }
            // write csv
            try (Writer cvsWriter = new OutputStreamWriter(csv, StandardCharsets.UTF_8.name())) {
                cvsWriter.write(header.toString());
                cvsWriter.write('\n');
                cvsWriter.write(content.toString());
            }
        }
    }

    private static void serializeElementHeader(StringWriter header, StringBuilder line,
            StartElement startElement) {
        header.write(startElement.getName().getLocalPart());
        header.write('/');
        Iterator<Attribute> it = startElement.getAttributes();
        while(it.hasNext()) {
            Attribute attr = it.next();
            header.write('_');
            header.write(attr.getName().getLocalPart());
            header.write('/');
            line.append(attr.getValue());
            line.append(',');
        }
    }

    private static String TEST_XML = "<?xml version='1.0'?>" 
            + "<Company>" 
            + "  <Employee id='1'>"
            + "      <Email>tp@xyz.com</Email>" 
            + "      <UserData id='id32' type='AttributesInContext'>"
            + "         <UserValue value='7in' title='Heigh'></UserValue>"
            + "         <UserValue value='' title='Weight'></UserValue>" 
            + "      </UserData>" 
            + "  </Employee>"
            + "  <Employee id='2'>"
            + "      <Email>tp@xyz.com</Email>" 
            + "      <UserData id='id33' type='AttributesInContext'>"
            + "         <UserValue value='6in' title='Heigh'></UserValue>"
            + "         <UserValue value='' title='Weight'></UserValue>" 
            + "      </UserData>" 
            + "  </Employee>"
            + "  <Employee id='3'>"
            + "      <Email>tp@xyz.com</Email>" 
            + "      <UserData id='id34' type='AttributesInContext'>"
            + "         <UserValue value='4in' title='Heigh'></UserValue>"
            + "         <UserValue value='' title='Weight'></UserValue>" 
            + "      </UserData>" 
            + "  </Employee>"
            + "</Company>";

    public static void main(String[] args) throws Exception {

        try (InputStream in = new ByteArrayInputStream(TEST_XML.getBytes(Charset.defaultCharset()));
                ByteArrayOutputStream out = new ByteArrayOutputStream(4096)) {
            convert(in, out);
            System.out.print(out.toString());
        }

    }

对于中等大小的文件，XML到CSV的转换速度尽可能快

1 个答案: